Signaling system



Dec. 26, 1944. w, MUEHTER SIGNALING SYSTEM Filed Aug. 3, 1940 2 Sheet-Sheet .1

I moie Ill .III.

INVENTOR. -M.W. MUEHTER ATTORNEY 1944- M. w. MUEHTER 2,365,719

SIGNALING SYSTEM Filed Aug. 5, 1940 2 Sheets-Sheet 2 RELAY SPECIAL ATTENTION T0 FIG. I

REGISTER N 9 ll.

INVENTOR. M.W. MUEHTER BY 4.4M

ATTORNEY Patented Dec. 26, 1944 SIGNALING SYSTEM Mani red WL'Miiehter, Npfley, N. .L, assignor to American District Telegraph Company, Jersey City, N. J a corporation of New J ersey This invention relates generallyrto signaling systems" and x more particularly m such systems used for 't nsmission'and rreceptionof fire alarm, n g l'arm'," watchm'ansl tour. and burglar alarmfsignalsfl v I f i. r. l'lheflsystem i a H artieulany adapted for auto: matically receiving signals of: the types outlined aboye,1 making a v record o f the signals and re: transmitting certain of the signals, such as fire andflpolic'efalarm signalsnto the fire or. police headquarters. Priorsystems have required manual retransmission and also manual attention during troubleconditionsj Q'Ihi's system provides automatic line switching and clearing apparatus for controlling and enabling the system to receive signals even though the various types of linen-fault conditions occuru Furth'ermore,-"- the equipment :functions withoutadjustmentwith any amount'of leakage on the line circuit pro: vided itis only'on on'e'side of--a"'transmitter in operation Prior" McCull'oh systems,- both man; ual and automatic, havlrequired rlayadjhstmerits, particularly during leakage conditions, these adjustments]necessarily distorting the signals andfr'equently changingto cause'loss of signals 7 V This system also incorporatesfa different" type or" signal which comprises break impulses and simultaneous mal ef andgroundimpulses, thereby eliminating the 1 prior inormal impulse which is necessary in McCullohfsystems of the old types. Elimination of the normalimpulses permits more of the line time-or "the digit time to be devoted to the other forms ofimpulsefs wherebyall impulses may beof longerjdurationI The transmitters used: in' the system are equipped with. can;

mutator type code wheels instead of. theusual pen spring type, therebyelimi'riating the necessity of an adjustment in the field and also maintaininga constant impulse ratio. 7

-Theprimaryobject'of the inventionislto provide anew and irnprovedpfintlal station signal receiving andj'etransrnittirig apparatus; t a v, ztnothel'iob'ieqt' of the' 'inyerition toiprovide' a -centraljstationsignal receiving, apparatus 7 parti'eular lyiadapted for automaticoperation. S ti IIaIlQlZhElTfOhjQQl; of this invention is to. prov de 1a fsi nalingj systmj which is {particularly adep'tedi for pa e1 ni ia esaM mwt operation.

troiilzglswherebyintelligiblesignals may S ti 11auotheriobiectoithisinyentionfisto pieepri'ipatibhvs sts, 1940, Serial No- 350623 1 i o 6 chum (Q 57 V i be receivedend ,retransin-itted during trouble conditions. v i

A further object of, this invention is-to provide a signaling system for eliminating false-signals caused by linecharging and dischargingeffects.

A still further object of the invention is to provide a new andimprovecl form-0f. transmitter and signal whereby delicate transmitter adjustments become unnecessary. i A still furtherobjectof thisinvention isto eliminate the necessity of adjustmentof line relaysduring line oribox leakage conditions. i H i; A still furtherobject of thisinvention'is topro vide a--signal-receiving system capable of retransmitting signals irom ,a 'shuntedbox or a shuntedloop. i H a l Astillifurther object of'this invention is to pro vide a receiving system capable of receiving signals from each side of a line circuit independently without the use of: ground signals.

"'rAStiH further object. oftthis invention is to providea signaling system capable of transmitting and receiving signals-ofrconstant impulse :ratio regardless of thelocation of the transmitter within the transmission loop circuit. l i

Further objects and advantagesof thisinventionwillberapp-arentto those skilled in the art after cohsiderationof the following specification taken in connection; with 1 the accompanying drawinggwherein: I

Fig. 1 is a circuit diagramillustratinga signal transmission'circuit together withthe signal re:

ceiving relays; r r a 2"is' 'a circuit diagram "of the timing and routing-relays together with a register: and I Fig. 3 illustrates the preferredform of transmitter codewheel which is used -in the transmittc honih l e c r i l. ,i fIhe' inventionjwill now be described generally in1order .to 'convey afgeneral impression; of the circuit :layout. The [system I is provided with transmission line I in the form of aloopj. includ; ing any desired number, of transmitters 2 Each transinitterv is equipped with a commutator type codewheel having successive conductingsegments therein, asiillus'tratedlin.Fig. 3 of the drawings. There are two-such codef'wheels in e'zich'tran's initteneach wheel being connected to oneside. of the transmitter loop. The two code wheels are electrically connected togetheron the same shaft and in addition a ground wheel is also v mounted on the same shaftfor the purpose of grounding the f transmitter wheels during their operatipn.- The ground wheel is provided with an undercut portion which normally or in the rest position removes ground from the code wheels. Referring'to Fig. 3, code wheel 60 normally rests in the position shown and rotates in the direction indicated bythe arrow. The segment 62 in each of the code wheels, together with the contact spring 6|, maintain the line circuit in a normally .closed condition whereby .asupervisory circuitis provided. When the code wheel 60 is rotated, the line is broken by the long space following segment 62, this space being followed by a prefix digit consisting of three make and ground impulses, as illustrated in Fig. 3 by way of example only. Each type ofalarmis-assigned a particular code prefix digit whereby the-signal may be identified at the central station. The prefix digit is followed by a space somewhat shorter than the initial break-signalrspace'whereby the central station apparatus may identifyathe first digit of the number code which follows the prefix digit. As the wheel filbcontinues its rotation, the number digits are transmitted 'untilthe long "break impulse at the ender the signal termina'tes the operation ot the central station-apparatus "and restores "the line circuit to normal when spring -61 contacts "the segment 62.

Signals are received at thecentral'oflice through theline and ground relays-L and G, respectively. The line and ground relaysfin turn control are- 'peating relay R. However, if trouble conditions occur'in the "line circuit '1 theB relay operates in the eventof breaksiinthe line and makes appropriate switching operations "for continuing relays L and Gin operation to control'th'e relay R. If the trouble conditions are in the nature of grounds either in the lines or in the boxes, the Q relay switches the windings the relay -R to render them operative under "the control of the relays Land "G.

In Fig. 2 of the :drawingawhe 'relayfl' :is a digit timing relay *which :ascertain's the end of 'each digit and the end (if-each :preflx, while therelay TT 'is a main timing relay for timing .the "duration of one round of signals and restoring "the apparatus to normal ifor rreceiving a succeeding round of signals.

The relays .X, Y and Z 'performfaroutingrflmntion and respond to war-iousiprefix digits :for routing special signals, such as :fire and police alarm signals to the fire and police headquarters transmitting .relays F. rH. Q.'and P. H. Q.

Relays 'U and V are (auxiliar switching :rela-ys for controlling the timing of relay andperforming other special :switching functions which will be described in greater detail in the iollowing:

LINE SUPERVISING CIRCUIT The normally supervised line circuit may .be traced from plus battery through .relay winding G], out through the line circuit 1. After passing .through the transmitters .2 of the line cirstead of the usual type employing pen springs. In the normal rest position of the transmitter the line circuits are closed between the two line brushes through the normal segments and hub on the commutator. In the normal position, the ground is removed from the commutator by means of an undercut portion on the hub segment. Afterthe normal segment, it will be noted thabithereiis a break equivalent to approximately three tooth spaces, which is to allow sufilcient time for switching operations, to be described at "alater point. After this break impulse the code LmayZbe cut as required.

ENORMAL CIRCUIT OPERATOR LF'IRsrBREAK IMPULSE Assuming .a transmitter to be in operation, at the time o'f'the first break impulse when the code wheel springs leave the normal segment, relay L .is deenergized .due to the opening in the .line circuit through its winding iL'l. "With release of relay FL, ;relay .3 is energized through circuits traced .from ground through'back contacts 2 of relay L, I2 of relay B, 8 or relay'Q, and winding BRto plusbattery. RelayB locks in through the circuit traced "through back contact 8 of relay Q, make contact 9 of relay ".8 to ground, 'later also "through conductor 10 and multiple contacts "5 of relay TT "and "5 or .relay T and make contact l'l "o'tre'layh. 'Re'lay R isen'ergized through the circuit traced from "ground through back contact 2 of relay "L, "through winding R2, back contact 'l5 of relay Q and 'l 'otirelay G to plus.

Tmmc RELAYS rRelay is energized at this time :through the-circuit traced from :plus, through make contact 5 ofrelay l3, in of relay 1B,, and =l0-of relay T, winding to ground. Relay FIT locks in edit, the circuit is completed .throughback con- OPERATION or .A TRANSMITTER Transmitters used -with this system are I equipped with commutator type code wheels ina digit of the code. 'The .delay on relay TT is' sufficient to prevent dropping out between digits of a code. With the release of .relay PI, relay X is energized through the circuit traced from plus through make contact 1 of relay R,'line.24, back contact 4 of relay Y, "I of relay 2, 9 of relay T,

and winding XI to 'minus.

LINE CIRCUIT SWITCHING At the time relay B operates, .the return side of the line ii is switched 'by the B relay-contacts through make contact 4 of .relaylB, winding LI, make contact I o'trelay'B 'to minus iauxiliary .battery. The application of the auxiliary battery to the "line circuit may produce a capacitive charging effect 'on th'e'line circuit of sufllcient intensity to cause amom'en'tary reenergiza'tion of relay L, momentarily deenergizing relay R. This, however, has no "effect on the operation of, the other relays, except that it .may slightly delay the release of the relay "T- and the energization of X just previously traced. With this switching operation the G2 "coil is removed from the circult; therefore from this point on the equipment snot affe ted; by Grelay,

any difi'erential action of the 'Emsr Gsou io IMPULSE V ,tOn the first ground impulse from the transmitter theG relay is energized through its windingGI to-plus battery, andrelayL isenergized through. itswinding LI to the minus auxiliary battery. ...Relay Ris releasechdue -to theopen circuit through its winding R2 at. back contacts L and G. Relay- X remains energized despite the opening of make contact I of relay R from plusthroug-h back contact 8 of relay R (this is a make-before-break type contact) line 25; make contacts 6 of relay X, line 26,-and I5 of relay-QB, back contact 8 ofrelay U and winding X2 to ground. At this time relay Q is energized through the circuit tracedfrom plus through make contact 2.-of relay G, winding QI, back contacts 1I -2. of relay Q, 9 of relay R, make con-' tacts I3 of relay B. and I of relayL to ground; Relay Q locks inthrough the'circuit traced from plus battery through winding Q2, and make-contacts 1B of relay Q, line 28, and '3 of relay TT to ground. :With release of relay R, relay'T is energized through thecircuit-traced from 'p'lus through make contact, 2 of relay TI and winding Ttoground. 1

i SECOND BREAK IMPULSE -Onwthe subsequent tbreak impulse,- relays L and G release'due to the open in the line circuit. This causes reenergization 'ofrelay R except that this time bothwindings RI and R2 are energized through circuits traced asfollows: 'From. plus battery throughback contact I of relay dame:

ing RI and make contact 2 of relay Q to'ground. Also from plus battery 'throu-ghmake contact 4! 4 ofrelay Q, winding R2, through back contacts of relay L to ground. 'With the operation of relay R, relay U is energized through the cirou'ittraced from plus battery throughmake contact Iof relay TT, line 29, make contact 4 of relay R, line 3U, back contact I of relay'Z, make contact I of relay X, winding =U,tand"r nake contaot4 of relay Toto ground. Relay'iU 'locks in through the circuit traced from plus through make con tact I of relay 'IT; I of relay U, windingU and contact 4-of relayTto ground. i i

' 'ICo'nE Iivrrutsnsjro REGISTER f. .OntheneXt (second) ground impulse, relays L, G, operate andR releasesas before. In addition the registerreceives an impulseatthistimedue to the fact that .relay I) has 'been energized. This circuit maybe traced fromplus through make contact Iof relay-"TT, line 29, back-contact 3 of relay R, .line 3], make contact 2-of relay U, through the register to ground. I y I On succeeding break and ground impulses ralaysL, G and R operate aspreviously covered to:

record the remainder of theimpulses of the code the automatic selection of headquarters retrans= 70 mission repeater circuits y CLEARING OPERA'noNs "A t the the e ode transmission along break [(minimxirh .of ,four. tooth ispaceshtakes place before the code springs/ complete the line cilfcuihat the normalsegment. During'this break relaysgLand ,Gj release as previously described causing energizationof relay R. Relay T releases after a short delay due to the shunt of contacts 5 of relay-R acmss its winding T. Relay TT also releases after a delay due to the shunt across its;v winding by the back. contact II of relay T through line 33; make contact I2 of relay'R and line 34,-and 2 of relay'V (the operation of'relay V will be explained later). The position of the slider of the variable resistor I5 may be adlusted for the required drop out time desired on relay l i 1 i Withlthe releasegof relay TT the locking circuit for.relayQis broken due to the open at contact 3 ofrelay 'I-, 3 of relay TI and 3 of relay Z. *(Re-" lays;-.Y andZ release due to opensin the vari-' ouslholdinglcircuits; to be explained in detail laterJ-J l Snoo'nn ROUND or SIGNALS Let' us assume that the, transmitter is a multiw round type, in which case as the transmitteris in ope'ration, the code springs in passing over the normal segment will cause the following opera: tions: Relays L and G-will energize, in turn caus-, ing release of relay R, and operation of relay Q, as previously'described, at the start of thelsig nali. "Relay 'IT will reenergize through thecir-. cuit" traced 'fromplus through back contactIB. of .relayR, line 33, back contact I! of relayT, winding TT resistor I5 togroundn RelayTwill energize through the circuit tracedfrom plus,

through make contact 2 of relayTT the resistor and winding Tto. ground. Thisrelay locks in through its make contact .I .of relay T, as before.

On the break impulse after this normal, relays Land G-releaseas before, causing operation of relayRn Relay'U is'energized through thecircuittraced from plus through make contact I of. relay line..29, make contact 4 of relay R, line 30, back contactJ of relay Z, make contact i of relay X,,winding U and contact 401" relayT toground at the same time a shunt is applied across thewinding of;relay T, by contact 5 of 4.01 relay T. i l

f CLEARING OPERATIONS The remainder of the round or, in the case of transmitters which have more than two rounds,

the signals are transmitted as previously covered up to this point. Onthe long breakiollowin-g the last round of the signals, relays L. G, R, .T,

lease of re lay R. With the energization of relays.

L and G, relay Q energizes. Relays ,TT and T energize through circuits previously traced. Shortly after the operation of relay T, relay TT dropsbiit dlle to th'e'shunt across its'winding 'ITby means .ofmake contact ll] of relay T,-and

backgcontact .I I. of relay R. Relay B releases due,

toppensin its holding circuits at various contacts 5 of relayTT, 5 of relay T and 8 .of relaylQ.

,-With the release of B, the line circuit is switched so that both ends are connect-ed to plus battery.thereby'causingrelease of relays L and G.

This circuit may be traced as follows: From plus battery, through winding GI, resistor 12, through thelinecircuit I returning through make contact:

6 of relayQ, back-contact 8"ofrelay B, relay-winding 11;], back contact 3 of relay 13, make contact of relay Q, and plus battery. Relay R is re"- energized through circuits previously traced through its winding RI and R2, causing energiza'tion of relay TT with the subsequent release of relay T which drops out after a short delay. This in turn causes the release of relay TT.

Relay Q next releases due to the open in its holding circuits through contacts 3 or relay T, 3 of relay 'IT'and 3 of relay Z. This switching operation returns the line circuit to its normal condition and the L relay picks up through its w-inding L1. The operation of relay L is aided at this time by current through its local Winding L2, this circuit being traoedas follows: From plus battery, through back-contacts 9 of relay TT, 13 of relay '1, line 35, 1601 relay Q, 15 of relay B, and winding L2 to ground. It will be noted that upon :release of relay Q and prior to the operation of relay L, the operating circuit of relay B is closed for a short instant. However, relay B is provided with a retarding winding 'BF, short-circuited by contact 6 oi relay B. This arrangement makes relay B slow operating and prevents its operation on the short impulse it receives. I

With the operation of relay L, the circuit through the R relay Winding R2 is interrupted causing the release of the R relay, which in turn causes the energization of relay 'I'I through circuits previously traced. Back contact 9 of relay 'IT opens and deenergize winding L2. Relay T also reenergizes with the closing of contact 2 of relay TT. This in turn causes the release of relay TT due to the shunt circuit across its winding by make contact 'ID of relay T and back contact I] of relay R. I

Release of relay R also breaks the circuit for relay X at make contact 1 of relay R, the other locking circuit through back contact 8 of relay R being open at contacts I6 of relay B and I! of relay 'Q. This returns all relays to their normal position and prepares the circuit for receipt of a signal from any other 'transmitter on the line circuit. Should a second transmitter on the line circuit start operation during these clearing out operations its operation will not be affected. The difference in this case being that some of the switching operations which take place at the start may be omitted dependingon the condition of the relays at the time the second transmitter starts.

OPERATION 'WITH LEAKAGE ON THE LINE CIRCUIT A leakage condition may exist on a circuit that is not sufficient to affect the -L or G relays until after retransmission starts. If this be the case, after the first operation of L or G when the line circuit has been switched for operation, either or both of these relays may be affected, as will be discussed below.

CASE 1 Leakage on :L relay side of transmitter The first case of leakage to be considered will be that of leakage on the line of sufiicient value to hold in the L relay preventing it from followin'gsubsequent break impulses of the t'ran'smitten However, we assume Directly rollowmg the operation 'ofrel'a'y 28, there fore relay L will reenergize. This is different troni the preceding description -for normal operation as relay L remained deenergized in that case during the total break impulse. Operation of relay L causes release of relay R due to the open in its operating circuit through winding R2 at back co'ntact L. RelayX now operates, thistime through the-circuit traced from plus through back contacts 8 of relay R,'line 25, 9 of relay Z and of relay 'Y, line 26, through make contact 16 of relay B, line 21, back contact '8 of relay U and Winding X2 to ground. On the first ground impulse from "the transmitters, relays G and "Q operate through the same circuits as'traced for normal operation. On the subsequent break impulse of the "transmitter to cause operation of relay R, relay X stays locked in through its winding Xi through make contacts -1 of relay R, line 24, and 6 -of relay X and win'dingXl. Relay U operat'ell as described for normal operation.

It may be pointedou t that if the leakage lsnot so strong as to make Lpick up upon application of the auxiliary battery to the line circuit, the operation during the first break impulse is as do scribed above for normal operation; otherwise the operation is for both cases as follows:

On all subsequent coding impulses o f the transmitter the relays and register operate as covered under 'Normal operation except as previously mentioned the L relay does not release at any time. During the long break between rounds of signals and when the code springs are passing over the normal segment, relays G, R, T, TT, Y, Z function the same as covered under Normal 'operation.

After the last digit of 'thecode of any round of a multi-round transmitter, the relays also function as covered under Normal operation upto the point where the B relay is deenergized. At this point, four conditions may exist as listed below:

1. The L relay may remain energized through the leakage and-G'deenergized.

2. The G relay may remain energized and L deenergized.

3. Both relays L and G may remain energized.

4. Both L and G may release as the leakage resistance may be of such a high value that the current will'be insuflicient to affect eitherrelay. In this case all clearing operations will be as covered under Normal operation.

Condition 1.- If the L relay remains energized after the line circuit has been switched by the release of the B relay, the remainder of theclearing operations takes place as follows: With the release of relay G, relay R is energized through the winding RI and make contact 2 of relay Q to ground. Relay T'I energizes with the closure of make contact In of relay "R, "through make contacts f3 of relay Q, I0 of relay R, 10 of re'layT and winding IT, through the resistor to ground. Relay T is shunted by make contact 501 rela'y'R,

and drops out after a short delay, in turn causing ceding one in that the G relay energizes and L remains deenergized'; due to" the leakage effect. The only difference'in operation will b that after the operation 01 relays R, T and IT, as previously described, relay Q will remain energized, through a locking circuit traced from plus through make contact 2 of :relayG, windingQl and make contact ll ofzrelayQ to-ground. .C'ondition 3. -This case considers the condition wherein the leakage resistance is low enough to hold in both the Land G- relays, in which case the difference from the preceding examples will be that relay Q holds in simultaneously through the locking circuits described for the previous two cases. i R does notenergize in this case andT remains operated while- TT drops after a delay due to the shunt across its coil-throughmake con-'- tact In of relay T and back-contact I l of relay R. Condition 4.-This caseconsidersthecondition where the leakage resistance is so high that neither the Lor G relays willhold in 'attheend cut oil. I With the operation of relay .G,- a circuit is closed from plus battery, throughmake contact 2 of relayG, winding Ql, back :contactslZ of I relay Q, 9 of relay R, of relay B, line 31,6 of relay TT and make contact I ofrelayT to ground, causing energization of, relay Q, which locks itself in through make contact ll of relay Q5 This' will-take place before relay 3 has-time to-operateasit did in theprevious cases, it being oft-he slow 3 operatingftypej When contact 8 of relay Q opensthe operatingcircuit o'f relay ;B,= its circuit is cut preventing operation at a later time. Relay 7 Q switches the incoming line circuits through 'make contact 6 ofrelay W, back contact 8 of relay B, winding Ll flba ck contact 3ofjrelay B and -make yontact' 5 "of relay Q; through 1 resist6r top lus battery, It will be notedthat for this case; the-:switching "oi -the line' circuit has placed both; sides of the line in" multiple td'plus' battery, whereas fin the previous case; the ftwo sides-'ofthe line" wereconnected between the plus main -battery "and the minus auxiliary, battery. After the energizatiom of relay Q yrelay R will energize through the'c'ircuit traced irom"p1us'bat'- term-throughmakecontact ll! of relay Q; winding R2, throughback contact 2 of relay L tojg'round. Operation of R causes to energize through' make contac tsl3 'of' relay Q; ID of 'relay Rj'line 22, and 'lflfof relay-TQ-j The remainder of the operation will be as, covered under the transmitter operation for theleakage conditions previouslydescribedencept that in this case the: signal retransmission depends on the'operation of relay L, relay G holds in on" the lineleakageg" '1 SHUNTEDTRANSMITTER .1 I,

Should anaesthet s is ta istic ans; or isfin alshunted loop be in 'operation, the first break impulse'iof ,the transmitter will have no effecton the relays; du l to the shunt. on the" first'g'roun'd impulse, relay w'inding G2 is'shunted' out, thereforethe G'relay'is energized by the currentthroughits winding GI and the ground at thetransmitter. Relay winding Ll also is shunted' out'by thesame ground but L may or may not drop out; depending on the speed relationship between itand the' operating time of relay Ge; In* any case, however, relay L will immediately reenergize through the circuit traced from plus'through makeco'ntact 2 of relay G, line 38, makecontact I-2 of relay T, line 35, back contacts 26 of relay Q' 'and I5 of relay B'and winding L2 to ground.--Relays Q and X energize through circuits previously traced for the'first leakage case,

that-isWh'ere the leakage affects the L relay except Xpicks up through contact I! of relay Q instead 0H6 of relay B. Otherwise the remainder of the operation is as covered under Normal operation, to thepoint where relays Q', Y-and Z release on the long break impulse of the transmitter. In thiscase, however, due to the shunt across'the box" or portion of the line, the line circuit isimmediately. restored to-its normal condition, with the releaseof Q, thereby causing reener gizationpf relay 'L through the normal line supervising circuit previously traced. From this point on the operation of the relays are as covered under" Normal operation, from the point where'Q releases causingenergization f L.

.O E A IQ WITH C U TIN.

p, TROUBLE CONQITION OPEN CIRCUIT CONDITIONING OPERATION Should a break occur in the line circuit the L relay will release" dueto the open in the circuit-of its winding Ll. This in turn causes operationoi relay ,Bthrough the circuit traced from plus through winding BR, through back contacts 8 pfrelay Q, l2 of relay B and, 2 of relay L to ground.;,, 7 Relay. B locks in, through the. circuit traced ,frorn .plus battery, through winding BR, back contact 8v ofrelay Q and make contact 9 of relay B to, ground. Simultaneously relay R operatestthrough ,the circuit traced from plus battery through backcontactl of relay G, back contact i ofrelay Q, .windingR2 and 'backcontact 2. of relay L to ground. 1 ,Relay TT is energized through make contacts 5 of relay B, It] ofrelay R, line.

'22, til of relayr T, WindingTT and resistor to ground. At the same; time a;-shunt is appliedto relay 'I by contact 5 of relayR, which causes its release after a short delay. With the release of relay T, relay TT drops out, due to the shunt across its windin by back contact ll ofrelay T,

line 33, make contact 12 of relay R, line 34, and

L1 TRANSMITTER OPERATION Shculd, a transrnitter start operation; on either, sideof the open its ground-impulses will control theoperation ofeither the L or Grelays. In the case of the L relay, the coding impulses will be transmitted from the transmitter ground, through the line, make contact} of relay B, winding Ll,

makecontactj of relay B, and resistor to minus auxiliary battery. e

Onthe'other side oithe open the line coding circuit" extends-f from the. transmitter ground through winding'Gl to plus mam battery.

Oh th r a hha e i t ha er-h tter either relay not GI operates, causing release or relay'R. by breaking the circuit through'its wind ing R2; The reinainder ofthe code operationis the same as covered under Norni al operation}! except that only one of the line relays will p coding, causing operation of relay R. Relay Q is not energized. At the time of the long break at the end of the round of signals, either relay. L or G will release, causing operation or relay R1, This'in turn causes release ofrelays T, TI, and Z as previously covered. as the code springs pass over the normal segment, no change takes place infthe linerelays due to the fact that the line cir- Quit, han The. t ha ht t hf the r unds o he' ltiima rah th tte 9 tra mitted n h a v ath d mann r 391 e en es e l f h he he r a-as t th l break hti ht en heath. 39

U D D BQUh-l" hhii N:

GROUND CONDITIDNING OPERATION.

Should a line circuit become, grounded, that h h w shi t he w e l ma w erie It in}; operation of'relay byfnrans of windin If. Theeircult for operation of G'may be d rom his ttt rs t thhh Wih'dih through'the li'n'e' dictate the ground. Relay Q then energizes through the circuit traced from lus battery, through make contact 2 of relay G, ha 1 1, hath tzhtae s l Qf: rel y Q, 9 f relay I4 of relay B, line 31, Q of relay TT and make contact! of relay T to ground.

Relay L is temporarily shunted out by the ground on the line circuit but reenergized 'upon' the operation ofrelay G through its local winding from plus through make contacts 2 of relay G, line 38, and ll of relay T, line 35, back contactslli of' relay Q- and l5-of-relay B, and winding L2 to ground. This circuit is opened, as contact l6. of relay Q opens, but at the same time the plus battery is applied to the return side of the line through make contact 5 of relay Q, back contact 3 ofqrelayB, winding Ll, back contact 8- of, relay B, make contact '6 of relay Q andline I, enabling L tov remain energized through the round on the line.

The, operation of. relayQ causesl operation of relay energizing. windingXtthrough a circuit, racedi rqm p us throuehbreak contac 8 ofirelay t, inet fi, .0. re ay Z, 8 of relay li clli, cone. act. l Qi lay Q l ne 21. ba k ontact Boirclay Hand w nd n Kite g ound- N -ha Q hhh t On t e first. eak mpulse o a ode si a either L or Gwill release depending on which side oi theground the transmitter is operated. This causes energ zation of relays Rf and 'TT and re lease of relay T in asirni lar manner to that de scribed for other signals. On the first ground impulse of the. first, digitot thecode, the deenergized line relay L or G reenergizes, causing re- 1 lease offrelay R and ene rgization of relay T. The remainder of the code, is transmitted in a sirnilar a bpi h j 1h tu ntwt e' h ieithtioh Qt. relay,

T the tat -eat n rele se at T1; thmhah all es rrtriohsiy treeest ter the ether eases OPEN GRoUNn'rRou m CONDITION CIRCUIT Comma Qr thrw This trouble condition consists of an open on the outgoing side of the line circuit with aground on. the return side of the open. The outgoing side of the line circuit-is that which is connected to battery at the central station.

- Gate 1 99th firs -e this case we will on i the c a t t on Where the. h reak hor y. precedesv the mllhdt Oh i br ak n the i e i c it, relay s wi l; r a aus ngoperation o re ay B. and n t a i r la s. B. T d in a si i ar mahhh 9 hatv desc bed. tor e n circuit r u l Qo d hh- Rela s T and TT may then re ease a a hhe mahh ii r sufii ent ime ela ses efore he round Qm on h ihe- When hi hheha 0.11. he etu the or h s xam e L relay will reenergize through this ground through make contact 4 of relay B, winding Ll, hat? tilhth 1 Qt elayr st r; o t e. minus auxiliary battery. This causes release of R due to the break in. the. circuit of windingR2, at back contact 2, ofrelay. L. Releasev of R energizes relay T'I it it has previously released, through the circuitv traced trom. plus through back con-v tact l'3.-ofrelay R, line. 33, back contact [I of relay T, winding TT' and. resistor to ground. Glosing 0t contact 2' of relay energizes relayI' through circuitapreviously discussed, this in turn causing release 0t relay TT. Relay X; staysv energizedfrom plus throughbackcontact 8; of relayR, line 25, contacts 6. of relayX; line 26, Ii of relay B, line 217; back contact 11 of; relayv U; andwinding- XZ to ground.

x es hlh h a, transm t er qre a on he erquh ltd; hit qt.- ah ath he fi s b a 1 iu s re athre ea a i han; ene z n R, deterrent-lithe im ar; manner-T 0 h t (it Qt hed r the 09%: t rhiiit; rouble ndi n- Q. the first thhh w itet he cod rel y eehah iha a a ea e Q relay R aha qrz a ien ia a .i z hu mehhet tq t a a tlh t te -t Th e haih laho he, o e w l e raht hitte at t9ver htler-Qn h r u tee at ht xtentwh n the PQQ W P- a v at e hq malse h ehti at e e tt t h r n qht he h rde. rel h eher zee t u thhtt h hleQath th wz hh a n aleae qt e a Rwhhauhawe t i h rsiza t relays. and throu h, circuits previously rag dy Ehtts hat ta it e art' caus r e se of ar es eb shihsthashuh r -m qe t l 910; l e a;.-13 htt eth teeth-ht ai p a R- q os e wh ti' a rah m teat be. i pe i o th a siftle 9 t h a e hah wi ake Plate on the transmitter operation until'the first ground Winding 1; ter g i, circuits. previously traced. The operation of coi'itact 8 ofrlay Q breaks the holding circuitfonthaBrelay, causing its release,

hetehr witthihe h iha elarw h i L from he a ihihatyhatteh th, h me h ,hetter hthe. firs rea h pt serelarq e se ne enere fhja ieh i. re ay ai hi ash its winqih' 'iat and. helsettttaet tl l-ip e ar a a ers 1 7. @EQU asotrzro energize in succession through CiI'CUitSjPIBViOHSIY traced. The remainder of the operation is as covered underground circuitoperation except at the time-thetransmitter contacts. close onv the normal. segment. Asin thiscase the line is open, the contactclosureon the normal segment produces no further ,effecton the line relay Q, R and X remain energized. I u v l A Case 2 r In this case we will assume that a ground occurs slightly before the break, in. which case the switching operation takes plac to conditionthe line for transmitter operation as covered under grounded operation. l

On-the ground the G2 relay Winding is shunted out 'as preyiously described, thus-causing operation ofrelay G, through-its windingGl and the ground on theline circuit to the main battery,

this .inturn" causing operation of t e re ays Q A and XQ- Whenthe open' occurs, for this case on the-outgoing side of the line, relay wil1;r elease, causing energization of relay B, through the ;c ir cult traced from p'lus through back contact I of relay G, Winding RI", and make contact 2 of relay Q to ground; Relays T; and TT. function in the same manner as covered in other cases for the firstloperation'of relayRQ t V I Assuming a' transmitterfto be in operation on the groundedside of the line, the first break impulse will cause "release of. relay L, which in turn causes release ofrelayQ' by breaking its holding circuit throughwinding Q2 at the make contact L. 'Rela'y (B I will energize through theoircuit traced from plus, batterythrough winding BR, through back contact '8 of relay Q, back contact l2 of relay B, and'ba'c'kf contact '2 .of relay L to ground. f3 locking in through the operation of its make contacts ll of relay B and? of relayB, 0n the first ground impulse, relay L reener'gi'zes', causing release oflrelay -R. The remainder of the operation taking place as covered under Case 1, with a transmitter in operation on, the grounded side ofjthe line. i

. Assuming a t H e s d en t e f t g ou d m se if a transmittenwill cause energization of relayG by means of. 'windingGl to plus battery. flhis in return causes release of relay B, by the break at back contact I of'relay Or. I Relays TT andT energize through circuits" previously traced The rem nd f e bpra n' llbe l d st 'd irbm ROUNDED Inqthis case we will assumethat the open occurs beforetheground inpoint of time. At the time of the opentherelays switch-exactly as covered;

under fOpen circuitoperation upto the point. where relay TI releases and X. is energized At, this time wewill assumethat the ground occurs, this will cause, energizationofi relay: G through its vtindingGlf to plusrnain battery.v The subsequent functions of A the relays-R, IIYT, T and X are-the s me; as. for Case; 14, under. the open ground con; dition. g, t ,Transmitter operationron either. side-of the line is similarto, that, covered under Open ground. operation.y 1 I .y 1 r,

For this ground open condition we will assume that "the groundoc curs shortly beforethefopen'. In'this'caserelaysG,Q and X are energized as covered under Grounded operation. 'On "the" ansmitterfi n, operation" on the ROUTING OF SIGNALS -In addition to-the relays used for line and register control, 'threerelays-namely, X,- Y and Z areutilized for the purpose of routing the various types of: signals. These signals are of the four classeslisted belowz v 1 A v 1-. Special Attention 3L FirezAlarm 4. Routine r SPECIAL ATTENTION SioNALs v -Signals which require special attention by the operator will record on-the register withthe first digit asa 13 The codewheel of the transmitte'r, however, will be cutwith two teeth as has been previously explained; the effect of the first tooth of-the code is eliminatedby the relays.-

On the first break or'groundimpulse, depending on the line'circuit' condition or during switching arrangemen'ts --to condition the line circuit forproper'operation the-X relay is energized as J previouslyooveredinthe'description. As previ ously explained, relay R ener-gizingon the break impulse followingthe first-ground impulse of the first digit causes operation of relayU; 'To-re- View,-=this circuit is traced from -plus through make contactz l ofrelay TT, line 29, make contact lI-of relay R, line 30,back contact I of relay Z, =makecontactil of relay winding U and make con'tactl of relay T to ground. "Relay U looksinthrough its make contact I of relay U. Uptocthis time any coding circuitthrough the register hasbeen o'penat'make contacts 1 and 2 of relay U, l of relay Y or'2 of relay Z. On the second ground impulse of the code when relay 3 releases, a'circuit'iscompleted to the register which maybe tracedfrom plus battery; through make-contact I of relay TT, line' 29, back contact 3 of relay R,:line 3|, make'contact 2 of relay U, through the :resistor and register coils to ground; Atthesame'time relay X releases as itsholding circuit" through windirigXl is broken at make contact :1 of relay R andthe holding circuit through winding is broken at back contact 8 of relay'U. I

On the next break (two-teeth being removed on thecode wheel afterthefirst digit); relay T- has time to release due to theshuntfleffect of contact 5 of relayR across its winding 'I-.- -This inturn causes'release' of relay U due to the opening of contact 4 ofrelay T in its circuit. At the same time, an impulse is initiated to a special attention relay through the circuit traced from ground'through back contact 5-of relay-'U, make contact 3 of relay Y'an'd'relay'SB'. On'the subsequent release of-relayR on' the next ground impulse, an im pulse for the second digit is transmitted through the register through the circuit previously traced,

- except this time through'make contact! of relay impulse of the code, relay Y is energized-through'the circuit traced from plus Y insteadcf. 2'0: relaysUz. Mir-the same timer'thc relay: Y locking. circuit is. established through win-ding Y2; from plus; through the; back con.- tact' 8; of relay. R, line- 253, make contacts .T: on relay T'I, 9'01: relay Y' and winding-'Ymtogroundi Realay X cannot be reenergized at this; time through winding X2 due toopenatcontactsj of relay X, 8 of relay Y" and make contact 1' of'relay U. At this time relay V is; energized; from plus: through ack; c n c s]: of re y 'Rr and: lot relayill, cornv tact 21 of; relay Y, and-windingflll: to.grcund-.. Re.- Iay V locks in from-plus through contactsl'li Qfare, lay TT and of relay V and windingawi to -round. This relay operates its OOIltfiCfiiZiQfiliGlfiYY thereby introducing resistance into the shunt. circuit of relay 'I'I through back contact; [ill of: relay T,

line 33, and make contact l2 of relay. R;,reducing its time delay. This is preparatory to the release of T1 during the long break at the end cf;the:code., Breviously this-shunt:acteddirectlyacross thecoilof TT. resulting inlonger delay; n.v order toprevent from droppingutduring thefairl long. break after the firstv digit. caused by the. r moval of. twoteetln on. the ode; wheel. Without this arrangement. a. longer break than now used wouldbe; necessary at. therends of the co e where. a minimum. offo rteeth isremoved. resulting in reduced. code, capacity. It is tobe noted that. only; one tooth is; removed. between succeeding digits so-that. the-treduceditime-delay of'TT will still be-sufficientto-keep-it; energized during the longer breakimpulsesbetween the following; digits.

On the subsequent; energizationsof R, on-the firstbreak.impulserotthesecond.digit..no-urther changetakes place in the routing relaysqas the. circuit of the winding; XI is open; an contacts 1' of relay-X and-backccntact 4 of, relayY andthe circuit to winding Zlt is open; at, make contact, 5; of relay X. Relay-Y stays-lockod-in:throughithe previous. locking circuit, traced from plusv throughmake contact 1 of, relay R,,line; 2.4, makeoontact- 5- of relay Y, break contact-870i; relay Z, winding Yland; make contact. 4r of. relay. TI! to% ground; During; groundimpulses when; make-contact T of relay R- is open and back ccntactzli-ofrrelayvn is. closed, relay is; held. energized: from plus through, back:contact 8-01.- relay R, line:2&, con;- tactsfl ofrelay TT and;9 'of[re1ay:Y. and winding Y2 to-. ground. The remainder on thee digits,- of: the,code,aretransmitteddnto:there isterthrough; make contact I of relay Y. instead; ofzi of; relay, U and cause no further change in thmmuting relays.

-At the completion; of. the, signelirelagYr is- (185 energized due-to the lopening ofoontant 4 ofsmlax causing operation of, relay.- X; from; plus. through make, contact, I! of; relay- R, ,line. 24,,back: contacts t of; relaylof; relay Z 4;- of relive T. and Winding XI to ground, Relay/V.- releases due; to the; opening of contact |O.f=. IG1ay nattention relay whose operation willbe: described at a,- later oint. remainsvlockediini. This;relayt initiates a: buzzer and; lamp. signal. to; indicate; thatvv the, supervisorfs attention. is reduired-2fon the: parti ularsignal transmittedr.

POLICE SIGNALIS" Asignal froma transmitter which iteqlliresthea attention of thev Police; Department will: havethe; first. digit of, the. coderecordqas-aafit, the code; wheelof course being-cut asfprev-iously described... with an extramooth.imtheiirstdigit, Theonerm ticnoi. the, routing relays. will bathe same-ascorered, under Specialattention sianals unto.- the,

point: where relay 2' is: energized. As: the: next ground impulse occurs after the regular break space; relay T does not have suflicienttime to release beforerelayR rel'easez Relay'Rk-sends a seconct impulse to the register for the, first digit ofithe cod'e. At the'same time relay:X'i's energized through the circuit traced as follows: from plus battery, through back contact 8* of relay R, line 25, back contact 9 of. relay Z, make contact 1 of relay Y, make contact 1 of relay U, and winding-X2 to ground; 0n the: subsequent" break impulse, which will be of? longer duration; relay Z will energize through the circuit traced from plus battery through make contacts T of relay R, line 24, 5 of relay Y, 5 of relay'X, and operatingwinding Zlto ground. Relay Z locks in throughthe circuit traced-fromplus battery through make contact lof; relay'TT, make contact H of relay z and winding 22"- to ground. Ree lay-T releasesaftera short delay deenergizi'ng relay, U. 0n the first ground impulse of the seconddigit relay V'is energized. These operations are-the same asexplained. in the previous case;

No further Change takes place in the condition of the routing relays due to open circuits iILthe circuits'of the various operatingwindings; The remaining digits of the code. are transmitted to theregister through circuits previously traced and'in addition routedto terminal l3 Where they control retransmission to police headquarters reheater-relay P. H. Q. This circuit may be tracedfrom ground through back contact 6 of relay R, line 40', back contact 4 0trelay U; make contact. 5jof'relay Z, make contacts 8.0f'relay X, and III of relay' Y to the policeheadquarters. The .circuit. controls the retransmission over a head quarters circuit. The circuit to the Special attention terminal [2' is also closed as described:

in the previous case.

FIRE ALARM SIGNALS- cutting thecode Wheel with four teeth to cover the elimin'ation of thefirst impulseas-previcusly described: The operation of all, routing relaysis" the same: as covered under Police Signals upto' the time of: the second break impulse of the. code when; the Z relay is energized.. This im- 'pulse is-0f ordinary length, thereby not allowingsufficienttime 'forrelay'T to release when during, the next ground impulse relay R releases. Relay X deenergizes. as; its. holding circuitrisopen at back contact 8 of relay U and back contacts 9 of relay Z or 6 of relay Y2 At this time a third impulse will: be transmitted to the register through circuitszpreviously. traced. On the following: break impulse relay R operates again-and relay-Y releases,- as=its holding circuit isopen atback contact 8- of relay 2' and make: contact 4 of relay; X: Due to the longertime betweendigits, relay '1? has time to release; irrtum causing release of; relay U1 as prev-iously described; On

V isenergized this time throughcontactof relay Z instead of 2 of relay Y.

The remainder of thedigits of'thecode will be contact, f, relay X, to. the fireheadquarters re-- peatenrelay, Q. At theesame-time, especial attention signal, is. initiated. through: the circuit.

the first ground impulse of the second'digit; relay traced from ground through back contact of relay Switch blade 5 Which will now be in relay U, make contact 6 of relay Z and back contact 2 of relay X to the special attention relay 50. Contact 2 of relay Z being closed, permits 'the remaining digit to be retransmitted to the register.

NIGHT WATCH AND ROUTINE S GNALS These signals have a 4 or higher number as the first digit. In this case all selector relay operations take place as covered under Fire --alarm signals up to the point where relay Y releases. Due to the fact that the particular break impulse is of normal short duration, it is not suflicient to allow for release of relay T. On

the next ground impulse relay X is again energized through the circuit traced from plus through back contact 8 of relay R, line 25, make contact Ill of relay Z, back contact 6 of relay Y,

make contact I of relay U, through winding X2 to ground. On the subsequent break impulse at the completion of this digit relay X remains energized through winding XI and contact I of relay X. For additional ground and impulses for TROUBLE INDICATIONS OF OPEN LINE CIRCUIT A trouble indication will be initiated through the circuit traced from ground through back contact I of relay Q, make contact 2 of relay B, in multiple with back contact 2 of relay T,

through resistor and the trouble light through switch blades FS/ I and SS/ I in the normal position to the trouble relay. A parallel circuit extends from the above mentioned relay contacts through switch blades SS/2 and FS/Z and the trouble relay. To silence the buzzer associated with this signal, the switch SS shall be thrown,

thereby causing release of the trouble relay but leaving the lamp lit by a direct connection to plus battery. Upon restoration of the trouble, the lamp is extinguished due to the open at back contact 2 of relay T and make contact 2 of relay B. At the same time the buzzer will again sound, this time a circuit being traced from ground through back contacts I of relay Q, I of relay B, switch blade S/2 in the right hand position, switch blade FS/Z in the normal position, resistor through the winding of the trouble relay to plus battery. To silence the buzzer the switch SS shall be thrown back to its normal position.

TROUBLE INDICATION-LINE CIRCUIT GROUNDED The trouble indication for this condition is initiated through the circuit traced from ground through make contact 2 of relay Q, through resistor, the trouble light and switch blades FS/I and SS/l, also through switch blades SS/2 and FS/2 and resistor T5, to the trouble terminal III to operate the trouble relay as previously described. Throwing the switch SS, connects the light directly to plus battery and causes release of the trouble relay to silence the buzzer. On restoration of the line circuit through the normal condition, relay Q releases, closing a circuit from ground through back contacts I of relay Q, I of all relays release.

the right hand position, switch blade FS/Z and resistor to again energize the trouble relay. To silence the buzzer the switch SS shall be thrown to its normal position.

For combination troubles of grounds and opens, similar circuits can be traced.

POWER SUPERVISION LINE RELAY PANEL FUsE In the case where a trouble, particularly in the local circuiting, causes blowing of the panel fuse, A circuit is then closed from ground through back contact 2 of relay T, line 4 I resistor, the lamp through switch blades FS/l and 83/ I, also through blades 88/2 and FS/Z and resistor T6, through the trouble relay to plus battery supply, which is not taken through the fuse, it being located on a separate panel unit. To silence the buzzer, the switch FS shall be thrown. This transfers the trouble light directly to plus battery on the main fuse and silences the buzzer. Upon restoration of the power by replacing the panel fuse after the trouble is cleared, the lamp is extinguished and a buzzer signal initiated through the circuit traced from ground through make contact 6 of relay T, switch blade FS/Z in the right hand position, resistor, through the trouble relay winding to plus battery. To

silence the buzzer the switch FS shall be thrown operator an indication of the nature of the trouble.

The preferred embodiment of the various parts of the above described system have been shown,

'but' it should be understood that further modifi therefore it is desired that this invention shall be limited only to the extent required by the prior art and the appended claims.

I claim:

1. In a signal transmission system, a transmission circuit includinga plurality of box transmitters, a line relay and a ground relay, a double winding repeating relay connected to contacts of the ground relay and the line relay for repeating signals from these relays, a source of potential normally connected to one side of the line and ground, the other side of the line being normally grounded, a code wheel and contacts at each transmitter for normally maintaining the line in closed condition and for transmitting a signal comprising break signals followed by simultaneous ground and make impulses, a break conditioning relay controlled by the line relay for connecting a battery of opposite polarity between the normally grounded line and ground in response to the first break signal, whereby the line and ground relays will respond to ground signals received on eitherside of the line during normal or broken line operation, a ground conditioning relay energized by the ground. and line relays in response to ground or make impulses, contacts actuated by the ground conditioning relay for connecting one winding of the repeating relay to the line relay contacts and the other winding of ,7 the repeating relay to the contacts of the ground relay whereby the repeating relay is actuated by break impulses on either side of the transmission circuit during normal or grounded conditions.

2. In a signal transmission system, a transmission circuit including a-plurality of transmitters, a line relay and a ground relay associated with said transmitters for relaying, signals therefrom, a double winding repeating relay having ,its windings connected respectively to contacts of the ground relay and the linerelay for repeating signals from these relays, .a source of. potential normally connected to the line, code wheel and contacts at each transmitter 'for maintaining the line in closed-condition and for transmitting a signal, a break conditioning relay controlled by the line relay for changing-theline connections to the source of potential in response to the first break signal, whereby the line and ground relays respond to signals during normal or broken line operation, a ground conditioning relay energized in response to signal impulses, contacts actuated by the ground conditioning relay for connecting the repeating relay in such as mannor that it is actuated by impulses from either side of the line during normal or grounded conditions.

3. In a signal transmission system, a transmission circuit including a plurality of box transmitters, a line relay and a ground relay, a double I winding repeating relay connected'to contacts of the ground relay and the line relay for repeating signals from these relays, a source of potential normally connected to one side of the line and sponse to the first break signal, whereby the .line and ground relays will respond to ground signals.

received on either side of the line during normal or broken line operation, a ground conditioning relay energized by'the ground and line relays in response to ground or make impulses, contacts actuated by the ground conditioning relay for connecting one winding of the repeating relay to the line relay contacts and the other winding of the repeating relay to the contacts of the ground relay whereby the repeating relay is actuated by break impulses on either side of the transmission circuit during normal or grounded conditions, a timing relay, contacts operated by the break conditioning relay-or the ground conditioning relay.

and the repeating relay and contacts operated by -a break timing relay for energizing the timing relay and contacts operated by the timing relay for locking the break conditioning and-the ground conditioning relay for the duration of the signal.

4. In a signal transmission system, transmission circuit including a plurality of transmitters,

nseam-.9

f line relayand aqground relay, a; repeating relay connected tocontacts of the ground relay and the line relay for repeatingsignals from these relays,

1 a source of potential normally connected to the line,code wheeland contacts at each transmitter for maintaining the line in closed condition and for transmitting a signal, a break conditioning relay controlled by the line relay for changing the line connections to the source of potential in response to the first break signal, whereby the line'and ground relaysrespond tosignals during normal or broken line operation, a ground conditioning relay energized in-response to signal impulses, contacts actuated by theground conditioning relay for connecting the repeating relay in sucha mannerthat it is actuated byiimpulses from either side of the line during normal or grounded conditions, a timing relay, contacts operated by the conditioning relaysand the repeating relay and contacts operated by a timing means for energizing the timing relay and contacts operated by the timing relay for locking the conditioning relays for the duration of a signal.

5. In a signal transmission system, a transmission circuit including a plurality of box trans mitters, a line relay and a ground relay associated with said transmitters for relaying signals therefrom, a double winding repeating relay having its windings connected respectively to contacts of ing relay for connecting the normally grounded side of the line to said grounded source of potential when the line is grounded and no break signal precedes a ground signal.

6. In a signal transmitting system, a code transmitter for sending a break signal followed by a make and ground signal, a repeating relay responsive to the signals, a timing relay responsive to the first ground impulse, a switching relay, contacts operated by the timing relay and the repeating relay for energizing the switching relay on the succeeding break impulse whereby the first ground impulse of any code signal is deleted to thereby delete impulses caused by capacity effects, a register and contacts operated by the repeating relay and the switching relay for operating the register.

MAN-FRED W. MU'EI-ITERL 

